Casey could be playing a game of: "if you want to talk to me, get me out of here, first"... to push her parents into bonding her out. Or, as others have said: she's playing the control game... it's all she has on her side, right now, to try to show who is running this game.
Or it could be, and this is a long shot: she's not talking to them, in a way to prepare them for a reveal... she's ready to tell LE where Caylee is at. But that is a verrrrrrrrrrry long shot and given Casey's attitude though, I'm back to the first paragraph I typed: I think it's the mind games issue and bullying her parents through whatever way she can control them.